WHY DOES MY OIL PRESSURE DROP AND VEHICLE FEEL LIKE IT'S GOING TO DIE WHEN AT A RED LIGHT?

2001 Chevrolet Tahoe • 96,000 miles

At the red light, the pressure will drop n fluctuate, then the other gauges drop n it feels, like it wants to die. Idle has a slight roughness, and the oil is at a good level. It's almost as if the alternator is bad and doesn't wnts to charge without help from a higher idle. But I've never seen that affect oil pressure. Please help!